1. Field of the Invention
This invention relates to a backlight module, more particularly to an edge-lit backlight module for liquid crystal display device.
2. Description of the Related Art
A liquid crystal display (LCD) device mainly includes a liquid crystal panel, and a backlight module for providing light to the liquid crystal panel. According to different needs, backlight modules are divided into direct back-lit backlight modules and edge back-lit backlight modules.
A conventional edge-lit backlight module includes a light emitting unit, a light guide plate, a back plate and a plastic frame. The light emitting unit has a flexible circuit board and a plurality of light emitting diodes that are disposed on the flexible circuit board. A portion of light emitted from the light emitting diodes is incident upon a light input surface of the light guide plate, and the remaining portion of the light emitted from the light emitting diodes travels to the flexible circuit board, the back plate and the plastic frame. Since the flexible circuit board, the back plate and the plastic frame have low light reflective efficiencies, the remaining portion of the light cannot be reflected thereby efficiently to the light guide plate, resulting in poor usage of light and a relatively low illuminating efficiency of the conventional edge-lit backlight module. To solve the abovementioned problem, luminous efficacy of the light emitting diodes has to be improved. However, this will lead to greater cost.